Effects of public posting on driving speed in Icelandic traffic.
A single daily sign showing percent of drivers not speeding cut average speeds 5 km/hr and halved serious violations.
01Research in Context
What this study did
Researchers put up a big sign on a busy Icelandic road. The sign showed the daily percent of drivers who were not speeding.
They tracked speeds over the study period. They used radar to measure every car that passed.
The sign updated each morning with the previous day's score.
What they found
Average speeds dropped 5.6 km/hr. That is about 3.5 mph slower.
Serious speeding was cut in half. Fewer drivers went more than 10 km/hr over the limit.
How this fits with other research
Phillabaum et al. (2023) did the same thing with clinic staff. They posted daily cleaning scores. Low performers quickly matched high performers.
Merritt et al. (2019) added tokens to public feedback. Staff tardiness dropped when daily scores were posted plus tokens were given.
All three studies show the same simple rule: post daily numbers where everyone can see them. Behavior improves.
Why it matters
You can use public posting anywhere. Post daily hand-washing scores in a school bathroom. Post percent of correct responses during social skills group. One sheet of paper and a marker can cut problem behavior in half. Try it next session: pick one skill, count it, post the percent correct, and watch improvement.
Want CEUs on This Topic?
The ABA Clubhouse has 60+ free CEUs — live every Wednesday. Ethics, supervision & clinical topics.
Join Free →Pick one group behavior, count it today, post the percent correct tomorrow morning.
02At a glance
03Original abstract
We replicated a study by Van Houten, Nau, and Marini (1980) that had revealed reductions in vehicle speeding following the posting of percentages of drivers not speeding on a sign at roadside. Our subjects were drivers entering a residential area where the speed limit changed from 90 km/hr (55.9 mph) to 60 km/hr (37.3 mph). A total of 4,409 vehicle speeds were taken from two observation sessions per day for 20 consecutive weekdays. The intervention consisted of a single posting condition, in which a hypothetical daily percentage of drivers not speeding was posted on a feedback sign, followed by a double posting condition, in which a sign posting a best result was erected beyond the feedback sign. Results revealed a significant speed reduction from an average of 69.0 km/hr (42.9 mph) during baseline to 63.4 km/hr (39.4 mph) during single posting. Average speed during double posting was 62.9 km/hr (39.1 mph). The percentage of drivers exceeding 70 km/hr (43.5 mph) dropped from 41.0 during baseline to 20.5 during single posting. The significant speed reductions add to the generality of findings of similar studies in Canada and Israel and offer possible explanations for the failure of feedback posting to reduce speed in the U.S.
Journal of applied behavior analysis, 1991 · doi:10.1901/jaba.1991.24-53